Radio diversity transmitter



Oct. 7, 14947. H. o. PETERSON Er AL l RADIO DIVVERSITY TRANSMITTEROriginal Filed May 2l, 1942 2 Sheets-Sheet 1 vlllllu'l' IN VEN TORS 01?/TPE/V01 fZ/wm e zo Pm T l m5 O u u R 4o e w E C o 0B H/ n o er w Y u l?.wm B Z; W H f THIVU n m ,s m c m V... KF@ y V W. JL T i Y 1 l`l m-IIE? Af W d? w R- 1 a o m 4 mm w y l /H m u Em e. m m m n` o Pw M A TTOR/VEI/0d 7., 1947- H. o. PETERSON Er AL 2,428,582

r RADIO DIVERSITY TRANSMITTER original Filed hay 21. 1942 2 Sheets-sheet2 GENERATOR INVENTORS Maro Pe'Cer om B er'narm rex/or MMM TTOENEL/Patented Oct. 7, 1947 2,428,582 RADIO DIvERsITY TRANSMITTER Harold 0.Peterson and Bertram Trevor, Riverhead, N. Y., assignors to RadioCorporation of America, a corporation of Delaware Original applicationMay 21, 1942, Serial No. 443,932.Y Divided and this application May 7,

1943, Serial No. 486,010

(Cl. Z50-17) 9 Claims.

Our present invention relates to communication or signaling on ultrahigh frequency radio waves and isa division of application Serial No.443,932, filed May 21, 1942.

When' signaling with ultra high frequency radio waves having, forexample, a wave length o'f the order of ten centimeters or la frequencyof the order of 3000 megacycles, it will be found that physicalobstructions cast rather sharp shadows.` This may be overcome bymounting the antenna'well above the physical obstructions. However,sincel it may not be possible, desirable or practicableI to locate asingle omni-directional antennaV above all nearby obstructions whichcast such shadows, it is an object of our present invention to overcomethis diinculty and to provide an omni-directional communication systemfor ultra short waves employing directive antennas, which system doesnot require unduly high supporting; structures.-

Also, as explained; in our parent application Serial No. 443,932, filedMay 21, 1942, when signaling with very short waves shadows or dead spotsare caused" byiobstacles in the path of the transmitted waves. Similardead spots are produced when short wave signals are transmitted from' aconsiderable Aaltitudejas, for instance, from the mast of 'a ship.` Forexample, consider two antennas of diiferent heights HI and H2 located ona tall` mast of a ship; The voltage,` picked lip-frein these two'antennas at varying distances froniithe mast is roughly indicated inFigure 1 brec the" solid line would indicate the variations yglialfstrength from the antenna at a height HZ andthe dotted line'lwould indicate the variatioris"iri signal strength for the antenna atthe height'HfI; f The zones'lo'flow intensity illustrated in Figure 1-`are pro'duced'by destructive inter- -ference between theY direct ray andthe ray riectedfromthe' eartlrs4 surface which, in the case' assumed,wouldV be 'the surface of the water.

'I 'he locations ofthe VZones of, low intensity depend "the wave length.and heights above ground ofthe'transinitting'and receiving antennas. Inaccodanc'e' with one aspect o'four-present invention, two antennas ofdifferent heights operating at the same or different frequenciesA areemployed tsub'stantalfly eliminate dead spots' or zones oflcfw'intensity"when` signaling on very short waves ofglfor'lexample,th'e `order of 3000 megacycles.

A It'isho'uld: therefore; beclear that one of the principalobectsof ou'rpresent invention is to provide improved ultra short wave` systems andAapparatus for overcoming zones. of low signal intensity` or deadspots?J Further objects, ad-

vantages and features of our invention will be apparent as the moredetailed description thereof proceeds. The latter will be given withtheV aid of the accompanying drawings wherein:

Figure 1 is a graph illustrating variations in zones of low intensityalong the earths surface for antennas of varying heights or for antennasoperating ondifferent wave lengths;

Figure 2 illustrates a transmitting arrangement for alternately excitingantennas of diierent heights so as to avoid the dead spots of Figure 1.It is to be noted in Figure 2 that the antennas may be excited withcarrier energy of the same or different frequencies; and

Figure 3 illustrates a modification of Figure 2 wherein pulses areradiated alternately from antennas. at two diierent heights and in twodirections. In connection with Figure 3 it is to be noted that'allantennas may be operated on the same carrier frequency, or each pair ofantennas may be operated at a different carrier frequency or, ifdesired, all of the antennas illustrated may each be operated on one offour diif'ere'nt carrier frequencies.

A` transmitting system for avoiding the loss of transmission due to theoccurrence of these zones of weak signal strength is illustrated inFigure 2. Tl'ietwo` antennas IIC and I 2C are arranged at dierentheights so as to have displaced zones of 'low intensity as illustratedinV Figure 1. That is to say, for' example, antenna IIC may be adjustedat such a height as to have the characteristic illustrated by curve HIof Figure 1 and antenna I2C may be adjusted to such a height as to havea characteristic illustrated by curve H2 of Figure 2 so that at alltimes within the range of the system` a substantial signal is receivedfrom either or both of the transmitting antennas. The antennas areYpreferably omnidirectionaland if placed on board ship may be of the typedescribed in Figure '7 of the patent application of J. B. Atwood, SerialNo. 441,659, led May 4,1942. The antennas IIC and I2C may, if desired,be directional over something more than 180 degrees and in this casethey preferably are of the typeV described byJ. B. Atwood in hiscopending application referred to and in' particular in Figures 3 and 4thereof. In

. this event, the antennas IIC and I2C of Figure of the radiated pulsesis that of the master os.

cillator MOI when switch SI is closed and switch S2 is open. Whentransmitting at different frequencies, switch SI is left open and switchS27' is closed, in which event the frequency of radiation from antennaIIC is that of the master or carrier oscillator MOI and Athe frequencyof radiation from antenna I2C is different, then being, when switch S2is closed, the frequency of operation of master oscillator M02. Thetiming of the radiated pulses from antennas IIC and I2C is controlled bya wave of super-sonic frequency generated by oscillator ISC which iscoupled. differentially to the and I'IC through transformer IBC. Thepulse modulators IEC and I'IC are excited cophasally with modulationwaves derived from microphone 20C and transformer 22C so that the pulseoutputs of modulator` 16C and IIC which at the frequency of the pulseoscillator ISC would vary in length or duration, as explained in greaterdetail in our parent application. It should be noted that the smallestsignificant signal element from the signal source 29C must be muchgreater in length than any individual pulse length generated by thepulse oscillator I9C.

Figure 3 shows a system whereby pulses are radiated alternately fromantennas at two different heights and also in two different directionsto avoid the interference of a local obstacle such as the supportingtower I of Figure 1 of our parent application Serial No. 443,932, filedMay 21, 1942. In the system of Figure 3 antennas 30 and 3|, supported atdifferent heights HI and H2, radiate in the same general direction.Antennas 39 and 40 are also supported at different heights HI and H2andare arranged to radiate in the opposite direction. If desired,antennas 39 and 40 may be arranged at heights respectively H3 and H4which are different than the heights HI and H2. The horizontaldirectivty of all of the antennas 30, 3I, 39 Vand 40 may be madeapproximately 180 degrees wide if effective radiationis desired in alldirections. In this event, each antenna may be made in the formillustratedfin Figures 3 and 4 of the J. B. Atwood applicationhereinabove referred to.

Transmitters or radio frequency power amplifiers 32 and 3,3 radiatepulses alternately, the timing being controlled by waves of super-sonicfrequency generated by oscillator 31 and fed through transformer 36 tothe pulse modulators 34 and 35. The pulse modulators 34 and 35, as

before explained, produce pulses of Varying h length, but of a frequencycontrolled by pulse generator 31. f

Transmitters or power amplifiers 45 and'46 also radiate pulsesalternately over the other antennas 39, 40, the timing being controlledby the same super-sonicoscillator 31 which, however, feeds the pulseYmodulators -41 and '48 through a phase adjusting network 38 andYtransformer 49. The phase adjuster 38 may be constructed in any knownway and is adjusted so as to produce a phase change such that the pulsesvradiated by power amplifiers 45 and 43 will occur midway between thepulses radiated by transmitters or power amplifiers 32 and 33,

All of the pulses are modulated cophasally orr simultaneously by wavespicked. up V0.11. micrq pulse modulators ISC frequency transmitters,power .amplifiers Vmodulators 32, 33, 45 and 46. When ajsimple l0VV ,anydistance and at any direction or height above `phone 50 and fed to allof the pulse modulators 34, 35, 4I and 48 through the secondary oftransformer 52. The radio frequency carrier wave is supplied by a masteroscillator MO5 which, when switch S3 is closed and S4 is open, supplieswaves of the same frequency to each of the radio or this is done,receiver will receive signal energy at ground within vthe range of thetransmitters 32, 33, 45 and 45.

. If desired, switch S3 may be opened and switch S4 closed, in whichevent the radiation from antennas 30 and.Y 3| will be at a frequencycontrolled by the master oscillator MO5 and the radiation from antennas39 and 4I) will be at a different frequency corresponding to thatderived from master oscillator MO5A. Or, if desired, a

separate master oscillator, each operating at a different frequency, maybe connected vso as to supply the transmitters 32,Y 33, 45 and 46 sothat the radiations from antennas 30, 3|, 39 and 40 will be of differentfrequencies. Where radiation occurs at different frequencies severalreceivers feeding into a common modulation or signal output circuitshould be provided each receiver having its radio frequency circuitstuned to a diierent one of the radiated frequencies;

yAs a further alternative, master oscillator MO5 may be used to controlthe radiation frequency of antenna 3l andV antenna 39 and masteroscilllator MOBA may be used to supply radio frequency waves of adifferent frequency to antennas 30 and 40.

Having thus describedour invention, what we claim is:

1. The method of` reducing Zones of low intensity when communicatingwave energy of the order of ten centimeters in length which includesgenerating a` plurality of such Waves of different frequency, generatinga signal wave in the form of Va train of recurrent pulses of apredetermined frequency simultaneously modulating-the generated waveswith said train and alternately radiating the Wave energies ofdifferent-frequency from points of,` different altitude at a'ratecorresponding to the pulse frequency. Y

2Q The method'of signaling which includes generating a radio frequencycarrier wave generating asignal wave in theform of a train of recurrentpulses of a predetermined frequency, modulating said carrier wave withsaid signal wave to obtain pulse modulated electromagnetic wave energyand alternately radiating the modulatedcarrier wave energy from pointsof different altitude at a rate corresponding to the pulse frequency;

3. In combination, 'apair of omni-.directional Y antennas :arranged atthe same geographical point Vbut having different altitudes, a sourceofelectromentalities for alternately feeding the pulse modulated waveenergy to saidV antennas at a rate equal to the pulse frequency. w

5. Y In combination, a pair of antennas arranged on electro-magnetic sat dierent altitudes, a source of electro-magnetic Wave energy modulatedby a train of recurrent pulses of a predetermined frequency, andinstrumentalities for alternately exciting said antennas with said pulsemodulated Wave energy at pulse frequency.

6. Apparatus as claimed in the preceding claim, characterized by thefact that said antennas are omni-directional.

7. The method of signaling which includes generating a radio frequencycarrier wave, generating a, signal Wave in the form of a train ofrecurrent pulses of a predetermined frequency, modulating said carrierWave with said signal Wave to obtain pulse modulated electro-magneticwave energy alternately radiating said modulated wave iienergydirectively'f'rom'a pai'rl'of points of different altitude at a ratecorresponding to the pulse frequency, and then radiating the Wave energydirectively in an opposite direction from a second pair of points ofdifferent altitude.

8. The method which includes generating a radio frequency carrier Wave,generating a signal wave in the form of a train of recurrent pulses of apredetermined frequency, modulating said carrier Wave with said signalwave to obtain pulse modulated electro-magnetic Wave energy, alternatelydirectively radiating in one direction said pulse modulatedelectro-magnetic wave energy Waves from a pair of vertically displacedpoints, alternately directively radiating in the opposite direction thesame modulated Wave energy from a second pair of vertically displacedpoints the rate of alternation being equal to the pulse rate.

9. The method which includes generating a radio frequency carrier Wave,generating a signal Wave in the form of a train of recurrent pulses of apredetermined frequency, modulating said carrier Wave with said signalWave to obtain pulse modulated electro-magnetic wave energy and ra- 6diating the wave energy from two pairs of vertically displaced points,the radiation taking place cyclically at a rate determined by the pulsefrequency. 5 HAROLD O. PETERSON. BERTRAM TREVOR.

REFERENCES CITED The following references are of record in the 10 fileof this patent:

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